1. Field of the Invention
The present invention relates to an articulated manipulator formed by joining a plurality of links by rotary joints. More particularly, the present invention relates to an articulated manipulator including a plurality of links, and joints including coaxial joints each for coaxially connecting the two adjacent links, and diagonal joints each for connecting the two adjacent links such that one of the two links makes a conical revolution on the diagonal joint.
2. Description of the Related Art
A prior art articulated manipulator disclosed in, for example, JP62-148182A has two links connected by a diagonal joint. The diagonal joint connects the two links such that one of the two links makes a conical revolution on the diagonal joint. Each of the two adjacent links connected by the diagonal joint revolves about a rotation axis inclined at a predetermined angle to its axis.
FIG. 10 is a front elevation of a conventional articulated manipulator 1. The articulated manipulator 1 includes a first link a1 to a sixth link a6, which are arranged linearly, and joints b1 to b6 connecting the adjacent ones of the links a1 to a6. The joints b1, b3 and b5 are coaxial joints, and the joints b2, b4 and b6 are diagonal joints. Each of the coaxial joints b1, b3 and b5 connects the two adjacent links so that the two adjacent links are able to rotate about their axes. Each of the diagonal joints b2, b4 and b6 connects the two adjacent links such that each of the two adjacent links is able to make a conical revolution about an axis inclined to its axis.
The articulated manipulator 1 formed by pivotally connecting the six links a1 to a6 by the joints b1 to b6 has six degrees of freedom. In the articulated manipulator 1, the coaxial joints b1, b3 and b5, and the diagonal joints b2, b4 and b6 are arranged alternately to connect the six links a1 to a6. Each of the six links a1 to a6 has one end connected to the adjacent link by the coaxial joint, and the other end connected to the adjacent link by the diagonal joint. The terminal part 2 of this articulated manipulator 1 is movable in a narrow space and the articulated manipulator has a small work volume.
FIGS. 11 to 13 are front elevations of the conventional articulated manipulator 1 having links a1 to a6. The position and orientation of the terminal part 2 of the articulated manipulator 1 are changed by turning the links a1 to a6. For example, the sixth link a6 can be moved in a direction parallel to the axis of the first link a1 with the sixth link a6 held coaxially with the first link a1 by turning the links a1 to a6 as shown in FIG. 11. The straight articulated manipulator 1 in which the links a1 to a6 are arranged straight can be bent in L-shapes as shown in FIGS. 12 and 13.
FIG. 14 shows the work volume of the conventional articulated manipulator 1. When the coaxial joints b1, b3 and b5, and the diagonal joints b2, b4 and b6 are arranged alternately, only the links connected by the diagonal joints b2, b4 and b6 can be bent relative to each other. Consequently, the terminal part 2 of the articulated manipulator 1 is able to move only in a narrow operational space T1 in a predetermined orientation. More concretely, the sixth link a6 is unable to move satisfactorily toward a base 4, remaining in a predetermined orientation. Thus, the terminal part 2 of the conventional articulated manipulator 1 is able to move in the narrow operational space T1 and hence the articulated manipulator 1 has a small work volume.